Controlling means for attaining equal speeds of two pistons working against resistances



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CONTROLLING MEANS FOR A'ITAINING EQUAL SPEEDS F TWO PISTONS WORKING AGAINST RESISTANCES Emil Biernath, Stuttgart-Unterturkheim, Germany, as-

signor to Schloe ann Aktiengesellschaft, Dusseldorf,

Germany Y Application June 11, 195s, serial'l No. 741,322 Claims priority, application Germany June 13,V 1957 V s 3 claims.l (ci. en -sz) 2,926,497 Patented Mar. 1,1960- ICC . 21 toa lever arm 22, which is rockable about afixed manner by coupling the pump shafts together for in stance, the desired aim is attained only approximately, but, from various causes, not with the necessaryy precig sion, for instance because the losses in thepumps and in the hydraulic drives of the two pistons differ from one another in magnitude when the resistances opposing the movements ofthe pistons are different.

This invention starts from a controlling meansfor the attainment of equal speeds of two pistons working against resistance, which are each driven by ahydrostatic pump provided with continuously variable means for regulating the quantity delivered. The invention consists in the feature that the branch, leading to one of the two pumps, of the delivery-regulating means common to the two pumps, can be corrected in dependence upon the difference between the speeds of the two pistons. The desired correction on one of the two branches of the deliveryregulating means admits of being accomplished in a very simple manner by the aidy of mechanical means, by the delivery-regulating means lacting through a rockable lever in each case upon the adjusting appliances of the two pumps, the etfective'lengths of the arms of one lever being variable relatively to the effective lengths of the arms of the other lever. The adjusting of the lever-arm lengths of one lever may be veffected by an adjusting motor that can be started forwards and backwards, and that can in its turn be started in one direction of rotation or the other, or stopped,'by an electrical relay. The controlling of the motor may however alternatively be effected by mechanical means in dependence upon an appliance measuring the differences between the speeds of the pistons.

- As already mentioned above, the controlling means according to the invention is adopted with special success when the two pump shafts are coupled together, for instance when they are driven by a common motor. In this case the correcting appliance serves merely to correct the differences between the quantities delivered by the two pumps at the same speeds of revolution.

The invention is illustrated by way of example in the accompanying drawing.

In a press frame 1, pistons 2 and 3 are movable in cylinders 8 and 9. They can be acted upon by liquid, which is delivered into the working cylinders Sand 9 through pipes 4 and S respectively by hydrostatic pumps 6 and 7. The pistons 2 and 3 are connected with slides 10 and 11, which are carried by press rams 12 and 13 respectively, the even running of which is to be ensured by this invention.

The press head 14 has a bore 15, into which the two rams 12 and 13 can enter, for the purpose of extruding through a die 16 the extrusion material located in the fulcrum 23.- The `upper end 'of the lever arm 22 1s pivoted at.24 to a rod 25, the other end of which is pivoted at 26 to a voltage-collector 27, which is rockable about a fixed fulcrum 28, which is connected by a conductor 34 with a relay 35. The free end of the voltagecollector 27 is movable over an arcuate resistance R1, the ends of which are connected by conductors 32 and 33 with the ends of a resistance R3, along which a voltagecollector 36 ismovable. Between the two conductors 32 and 33, and therefore between opposite ends of each of 'Y the resistances R1 and R2,'a potential difference isgestablished bya source of voltage such as a battery 29, connected with the said conductors by leads 30 and 31.

In the drawing the two voltage-collectors 27 and 36I occupy their mid positions, marked O. Fromthe relay 35 a conductor 35a leads to a control switch 38,` which, according. to the voltage transmitted to it, causes anadjusting motor 40, by way of a controlling conductor 39, to start in one direction or the other. When the -relayl35 is under Zero voltage it stops the motor 40 through the relay 38.' I

The adjustingmotor 40 receives current through conductors 41 from a source of current, and drives, with its shaft 42 through a slipping clutch 42a, a worm 43, which in its turn cooperates with a worm wheel 44. On the shaft 45' of the worm wheel 44 is mounted a toothed wheel 46, which meshes with an axially displaceablerack 47. Abutments 59 and 59a, which may also be adjust-v able in the direction of the rack 47, limit the upward and downward movement of the rack. When the rack 47 strikes one of these abutments, the clutch 42a slips. Upon the rack is securely mounted a rocking bearing 48, in which a control lever 49 can rock. Upon displacement of the rack 47 the bearing 48 is displaced along the lever 49, so that the effective lengths of the Varms 49a and 49b of that-.lever are altered. The upper end of the lever arm 49a ofthe lever 49 is attached to an adjusting rod 50 of the pump 7, while to the lower end of the arm 49b is attached a control rod 51. At the point 51a of the Qontrol rod is attached a mechanical appliance, notshowri, for regulating the quantity delivered by the pumps 6 and 7. The rod 51 can however also be displaced vby hand. To the other end of the control rod Slis pivoted thelower arm 52a` of an adjusting rod'52, the upper arm 52b of which is lin its turn pivotally engaged at 53 with the adjusting rod 54 of the pump V6. The adjusting rodsl 50, and 54 are not designed as mirror images of one another but are so constructed that the quantities delivered by the two pumps are increased for example when the two adjusting rods 50 and 54 are displaced towards the right. At zero delivery of the pumps the members 54/50, 49, 52 and 51 form a rectangle, as shown in the drawing, and no adjustment of the pump 7 takes place in this position by displacement of the bearing 48. The rocking bearing 55 for the lever 52 is undisplaceable. The two pumps 6 and 7 are driven by a common motor 56, through fixed couplings 57 and 58.

The apparatus works in operation as follows: When lags behind 'the piston 2, rthe pinion 19 pushes the rod 20 towards the right, as a result of which the rod is displaced towards the left, and the voltage-collector 27 is thereby turned ina counter-clockwise direction. So long as the voltage-collectors 27 and 36 remain in the zero position, the relay remains de-energized. Since however the voltage-collector 27 is now displaced along its resistance R1, while the voltage-collector 36 remains in its mid-position, a potential acts upon the relay 35 in such a manner'that it controls the switch 38 to start the adjusting motor 40. By the running of the adjusting motor the rocking bearing 48 is displaced, so that the ratio between the lever arms 49a and 49h Vis altered. Since the rod 51, duringthe pumping work, is not located in its mid-position as shown, there occurs, owing to the displacement of the rocking bearing 48, an axial displace ment of the adjusting rod 50 of the pump 7 which now occasions an increased delivery from the pump 7 into the cylinder 9 Iof the piston 3. In consequence of this increased delivery, the speed of the piston 3 increases until it has overtaken the piston 2. Under these circumstances the voltage-'collector 27 is at the same time turned back by way of the members 17 to 25, vso that the relay 35 becomes de-energized, and stops the adjusting `motor 40. Since, with the adjusting of the rocking bearing 48, the position of the voltage-collector 36 upon the resistance R2 has changed, the relay 35 is placed under voltage in the opposite direction, so that it starts the motor in the vopposite sense, and this motor now brings the adjustin'g bearing 4S back into its initial position.

By the abutments 59 and 59a the quickness of the regulating can be limited to a greater or less extent, that is to say, the speed with which the lagging ram, for instance 13, overtakes the leading ram 12, can be restricted. This is important in cable-sheathing` presses, since a too rapid overtaking would result in a poor extrusion product. I

In cable-sheathing 'presses with a low extrusion speed, small deliveries are required of the pumps. If Vwith a small pump delivery the voltage-collector 27 has va large deflection, the regulating, that is to say, the acceleration ofthe lagging ram, need not be effected so rapidly as with a large pump delivery. The regulating operation must therefore be dependent 'upon existing speed of extrusion. If for instance with a large pump delivery, that is to say, with a high speed of extrusion, a dlterence of 2 percent between the speeds of the two rams is regarded as admissible, then with a low speed 'of extrusion the diierence in speed in the `regulating should not be greater. This -is approximately attainable with `the controlling means according tothe present invention.

This example of construction may advantageously be modfiedin such a way that not only the bearing 48 but also the bearing 55 is longitudinally displaceable. The appliance effecting this must then be so constructed that one bearing is displaced downwards while the .other bearin'gis displaced upwards.

I claim: Y

l. Controlling means for equalizing the speeds of two hydraulic pistons working against resistances, for instancethe pistons of a hydraulic double-billet extrusion press, comprising: two hydrostatic pumps, each supplying pressure liquid to one of the pistons, two adjusting elements, one for each pump, for continuously varying the quantity of liquid delivered by the pump, a manually movable member, two levers, each connecting one of the adjusting elements with one end of the manually movable member, two bearings, constituting the fulcra of the two levers, one of these bearings being slidable along its lever, these levers being rockable about their fulcra in such a way that when the manually movablemember is moved longitudinally in onevdirection it acts upon the adjusting elements 'so as to increase the de1ivery of both pumps, and when it is moved in the opposite direction it acts so as to reduce the delivery of both pumps, and a control acting upon'one of the adjusting elements by sliding the ulcrum of its lever along the lever, So as to change the ratio between the effective arms of the lever in dependence upon the difference in speed between the piston associated with that lever and the other piston.v

2. Controlling means for equalizing the speeds of two 'A hydraulic pistons as claimed in claim 1, the control that acts upon one of the adjusting elements comprising: two electrical resistances, conductors connecting the ends of one resistance with the ends of the other resistance, a source of voltage interposed between the two conductors, a voltage take-off control movable along one of the resistances, means actuated by any difference in speed between the two hydraulic pistons for moving the control along the resistance, a reversible electric control motor, a relay controlled by current flowing in the conductors, this relay controlling the electric control motor, transmission means by which the electric control motor slides the movable bearing along its lever, a voltage take-off carried by the movable bearing and movable along the second resistance, and means controlled by this voltage take-01T for restoring the movable bearing to its normal `position when the lagging piston has overtaken the leading piston.

3. Controlling means for equalizing the speeds of two hydraulic pistons as claimed in claim 2, further comprisingz'abutments limiting the travel of the movable bearing, and a slipping clutch interposed in the,r transmission Y means between the electric control motor and the mov-y able bearing.

References Cited in the le of this patent UNITED STATES PATENTS .1,900,050 'f Emst Mar. 7, 1933 2,312,213 Ferris Feb. 23, 1943 2,400,685 Collins May 21, 1946 FOREIGN PATENTS 738,514 Great Britain Oct. 12, 1955 

